Process for the manufacture of 1,1,2,2-tetrahydro-perfluoro-alkanols

ABSTRACT

2-PERFLUOROALKYL ETHANOLS ARE OBTAINED BY REACTING 2PERFLUORO-ALKYL ETHYLIODIDES WITH AT LEAST THE TWO-FOLD MOLAR AMOUNT OF NITRIC ACID OF ABOUT 70 TO 98% STRENGTH AND HYDROGENATING THE INTERMEDIATES,WHICH ARE THE NITRATES OF THE DESIRED ETHANOLS. THE PRODUCTS ARE USEFUL AS STARTING MATERIALS FOR THE PRODUCTION OF HYDROPHOBIC AND OLEOPHOBIC TEXTILE FINISHING AGENTS, E.G. THE POLYMER ACRYLATES AND METHACRYLATES OF SAID 2-PERFLUOROALKYL-ETHANOLS.

United States Patent 3,824,296 PROCESS FOR THE MANUFACTURE OF 1,1,2,2- TETRAHYDRO-PERFLUORO-ALKANOLS Erich Schuierer and Klaus Ulm, Burghausen, Siegfried Rebsdat, Altotting, and Ignaz Wimmer, Unterau (Neuottiug Post Oflice), Germany, assignors to Farbwerke Hoechst AG, Frankfurt am Main, Germany No Drawing. Filed June 7, 1971, Ser. No. 150,770 Claims priority, application Germany, June 10, 1970,

P 20 28 459.7 Int. Cl. C07c 31/34 U.'S. Cl. 260-633 10 Claims ABSTRACT OF THE DISCLOSURE Z-Perfluoroalkyl ethanols are obtained by reacting 2- perfluoro-alkyl ethyliodides with at least the two-fold molar amount of nitric acid of about 70 to 98% strength and hydrogenating the intermediates, which are the nitrates of the desired ethanols. The products are useful as starting materials for the production of hydrophobic and oleophobic textile finishing agents, e.g. the polymer acrylates and methacrylates of said Z-perfluoroalkyl-ethanols.

The object of the invention is a process for the manufacture of fluorine-containing alcohols of the general formula R .CH .CH .OH,

in which R, represents a preferably straight chain perfluoro-alkyl radical having 4 to 16, in particular 4 to 10, carbon atoms, from fluorine-containing alkyl-iodides of the general formula in which R, has the same meaning as given above, which comprises transforming in a first step the fluorine-containing iodides with nitric acid having a strength of about 70 98%, in a molar ratio of at least 1:2, preferably about 1:3 up to 1:8, especially 1:4, at temperatures in the range of about 100 C., into the corresponding nitrates of the general formula R .CH .CH .O.NO

and hydrogenating them in a second step in the presence of the usual hydrogenating catalysts at temperatures of about 50l00 C. and pressures of about 0-100 atmospheres gauge to obtain the desired alcohols.

Fluorine-containing alcohols of the above indicated constitution have been obtained hitherto according to the process described in German Pat. 1,214,660 by reaction of the corresponding iodides of the general formula R .CH .CH .I with oleum and following hydrolysis of the fiuorine-alkyl-sulfate esters of the general formula R;.CH .CH .O.SO H. This process has the disadvantage that a considerable amount of the fluoro-alkyl-iodides used always passes into difiicultly hydrolizable di-esters of sulfuric acid of the general formula (R .CH .CH .O) .SO and that, in addition, the monofiuoro-alkyl-sulfate esters of the general formula R .CH .CH .O.SO H in the case of R;2C F are saponified essentially slower in aqueous sulfuric acid at 100 C. than the corresponding compound having shorter fluoro-alkyl radicals.

According to the process described in U.S. Pat. 3,246,- 030, fiuoro-alkyl-iodides are reacted with silverand mercury salts of nitric acid and the resulting nitrates are then converted by means of lithium-aluminium hydride or ammonium hydrogeno-sulfide into the corresponding fluorine-containing alcohols. However, for the manufacture on an industrial scale this process cannot be used owing to it high expenditure of silver or mercury nitrate and due to the necessity of recovering the silver and mercury from the metal halides formed during reaction.

The process of the invention is carried out in two stages which it is suitable to effect separately. In the first stage the corresponding iodide (-R .CH .CH .I) is reacted with nitric acid under formation of the corresponding nitrate (R .CH .CH .O.NO and iodine (iodate or iodine pentoxide, respectively, in the case of an excess of nitric acid):

In the second stage the ester (R .CH .CH .O.NO is reduced to the corresponding alcohol (R .CH .CH .OH) by means of hydrogen under pressure in the presence of the usual hydrogenation catalysts such as platinum, palladium, cobalt or nickel contacts on the usual carriers such as silica gel, charcoal, barium-sulfate, pummice stone or calcium carbonate, in particular, however, Raney nickel, to yield the corresponding alcohol (R,.CH .CH .OH) and ammonia.

Saponification with the aid of aqueous lyes is practically not realizable, because, in addition of a number of not identifiable products, the olefin (R;.CH=CH corresponding to each iodide is formed.

The starting materials for the process of the invention are fiuoro-alkyl-iodides having a fluoro-alkyl radical of 4-16, especially 4-10 carbon atoms. It is of advantage to use mixtures of such iodides which are obtainable, for example by telomerization of lower perfiuoro-olefins to perfluoro-alkyl-iodides and addition of ethylene in known manner. For the reaction in the first stage, nitric acid is used in a concentration of about -98%, preferably about -98%, and the operation is carried out at temperatures of about 20-100 0, preferably 6090 C. In the case of compounds containing a perfluoro-alkyl radical in the range of CE, or C F temperatures in the range of between 6080 C. should be maintained in view of the high volatility of the substances. The reaction sets in already at room temperature; for completing the reaction, however, it is recommended to raise the temperature at the end of the reaction to at least 60-65 C.

The molar proportion of fluorine-containing alkyl-iodide to nitric acid may amount to about 1:2 to 1:8 and more, preferably 1:3 to 1:8, and should suitably and preferably be 1:4.

The reaction may be carried out by two ways, either by introducing first the nitric acid and then adding, portionwise, the fluorine-containing alkyl-iodide or by first introducing the iodide in molten state and then continuously adding dropwise the nitric acid.

A preferred embodiment of the process of the invention is described hereinafter.

The total amount of fluoro-alkyl-iodide is introduced in molten state and the nitric acid is added dropwise, while stirring. The reaction starts rapidly. The nitrate formed as the reaction product is soluble in the mixture of the reaction partners. Iodine in elementary form is formed as a secondary product. The major part of its sublimates at the chosen reaction temperature and can be easily recovered after separation in a suitable cooling apparatus. After removal of the major part of iodine, water is added to the reaction mixture and the nitrate is separated from the aqueous phase. It is then dissolved in inert, low molecular weight, halogen-containing hydrocarbons, preferably in chloroform or methylene chloride. Residual fluorine-containing nitrates can also be recovered from the aqueous phase by means of chloroform or methylene chloride. The organic phase is still contaminated by low amounts of iodine and nitric acid. It is washed with water until it is free from acid and the iodine still contained therein as impurity is removed by pumping at about normal pressure or under reduced pressure. The fluorine-containing nitrates are obtained in the form of weakly pink coloured oils or solids (see Table I). They are not decomposed by water or excess of nitric acid; with compounds having a Rf radical of C 1 up to C F they can be easily purified by distillation.

If the reaction is carried out by introducing at first the nitric acid and then adding dropwise the fluorinecontaining iodide, the iodide separated during the hydrolysis passes immediately into an iodate or iodine-pentoxide due to oxidation by the excess of nitric acid. The fluorine-containing nitrate is precipitated also in this By the reaction with unsaturated organic acids, especially acrylic acid, acrylic acid and their ester-forming derivatives, valuable esters are obtained which after polymerization yield oiland water-repelling agents for textile materials.

The following Examples illustrate the invention:

EXAMPLE 1 (a) 110 g. (1.71 moles) of 98% nitric acid were added case by the addition of water. The aqueous phase then 10 a contains the iodine in the form of iodi c acid. Recove y 26 2 625; g g 'i ag 8 i g i If desired 111 known manner pletion of the dropwise addition, the whole was further ggg z gg g Second process Step i e the stirred for 8 hours at 70 C. The iodine set free during the reaction Sublimated from the reaction mixture, dehydrogenation of the fluorine-containing nitrate, care be as g 2? 3 323 21: g g zfi 2 3;? fi ggg z purification from this finger. The reaction mixture was allowed to Tliz hydrogenation is carr ied out with a view to cool 5 then c9mbined with of The practical application in a pressure range of about to 20 E 221 22 12 5 j fizggg fizze ii i it t 100 atmospheres gauge, preferably to 50 atmospheres u q m f d th auge As catalyst Raney nickel is preferably used in a several tunes W1 3 sma amolmt o c on) orm an e i of about 540% by weight preferably chloroform phases were combined. In order to remove 2 weight referred to the fluorineicontaining nitrate any present acid, the chloroform solutions were washed u ed As ieaction mediums lower alkanols especially 25 several times with p i of.water The orgamc methanol are suitable. The reaction is effected advanphase was p SubJeFted to dlstlnatlon At fi chloro' tageously in an autoclave made of stainless steel or an figg g 2 3 5 2952 Egg ig g i t i g i gs autoclave lined with silver. The reaction temperature is y p p d in the range of 50-100 C., preferably at 7090 C. The remammg twine gi g gg g re- After termination of the hydrogen consumption pressure 30 ggfgfi g zi gg-ig si g 2: in the autoclave is then released and the reaction mixd d d f 90 g 1 N 1 t d ture obtained is freed from catalyst by filtration. The z gg f g zz ca cu e solvent is then removed by distillation and the fluorine- 2 4 6 a 3 fi w g 'Q H ONO containing alkanols obtained are then purified by distilth thanol and 6 4 g g nzickel lation under reduced pressure. In principle, the hydrog6 W1 me 1 f 1 genation with Raney nickel in methanol is also possible muioduced m an .autoc i 0 Stam ess stee Afier without excess pressure at about 60 C.; however, the havmg mused several tunes wlth N2 and H2 was time needed therefor is three to four times longer for troduced at a pressure of 30 atmospheres gauge and about 3040 g of fluorine containing nitrate pressure vessel was then heated to 80 C. When this The proof of the structure of the fluorine-containing 40 temperature was reached hydrogenanon was i nitrate prepared can be made by comparative tests and at a pressure of p atmospheres gauge uratlon with the use of the infrared absorption spectrutns. If, 2 4 i After coohng and release of the pressure for example CGFlsCHzCHzOH (prepared according to any residues of the catalyst were removed from the German Pat. 1,214,660) is esterified according to known macho? {mxmre by .filiratlpn and then F l methods on the one hand with 98% nitric acid (cf. Examgg??? i fi g f g g ple 6) and on the other hand with nitrous acid (from mame e m mm W et Cory NaNo2 and H 2504 CL Example 7) two difierent liquid of n-C F C H OH were recovered by distillation at 73- products are obtained, 76 C./ Torr. (Analysis: OH number calculated for C H F 0:212; OH number found 211 CtF1 CHz.CHz.OH+HNO R omncmcinono, 50 6 5 9 EXAMPLE 2 CF|3CH3.CHQ.OH HNO2 CsFrsCHz.CH20-NO (a) 145 ml. (3.38 moles) of 98% of nitric acid were of which the first with regard to its characteristical data added dropwise at 80 C., while stirring, in the course (cf. Table I) and its infrared spectrum is identical with of 3 hours to 400 g. (0.845 mole) of n-C F C H I. The the reaction product obtained from C F CH .CH .I 55 mixture was then further stirred for 8 hours at C. and HNO The elimination of the iodine was carried out as described The fluorine-containing nitrates prepared according to in Example I. The fluorine-containing nitrate was sepathe present invention are characterized by the following rated from the mixture by the addition of 200 ml. of data: water. The further working up was likewise effected as TABLE I M It Refrtietliive Boiling point pointi (25 G Com ound:

4FoCzH4ONOz 50-60" C./12 mm. Hg

CoFraCzHgONOL- 72-77 o./ii mm. Hg ca.-20 C. CsFi1C2H ONOz -105 C./10 mm. Hg 345 C. 010F21C2H4ONO2- 74 0.

Comparative tests:

CflFl3C2H4ONO2 72-77 C./11 mm. Hg ea.20 C. 6Fl3 2H4ON0 49-58 C./11 mm. Hg 20 C.

1 Prepared according to example 6 from CQFHC2H4OH and HNO 3 Prepared according to example 7 from CQFISC2H4OH and HNOz.

The fluorine-containing alcohols prepared in this manner are valuable starting materials in the manufacture of oleophobic and hydrophobic agents and of surfactants.

described in Example I. The liquid reddish crude product obtained after evaporation of the solvent could be purified by distillation under reduced pressure. 314 g. 91%

of the theory of pure n-C F C H ONO were obtained at 7277 C./11 mm. Hg.

Analysis:

N calculated for C I-I F NO -=3.42; N found 3.40%

(b) 280 g. (0.685 mole) of n-C F C H ON together with 520 g. of methanol and 20 g. of Raney nickel were introduced into an autoclave having a capacity of 2.5 liters. After having rinsed several times with N and hydrogen, hydrogen was introduced with a pressure of 30 atmospheres gauge and the autoclave was heated within 2 hours to 90 C. When this temperature was reached the pressure of hydrogen was increased to 50 atmospheres gauge. The autoclave was then shaken at 90 C. for 6 hours, the pressure of hydrogen being maintained constant. The hydrogen consumed was replenished from a pressure bomb. The pressure vessel was then cooled and emptied. Any residues of catalyst were removed from the mixture by filtration over folding filters. After removal of the methanol used as the solvent, the desired product was obtained at first in the form of a fluorine-containing, crude alcohol. This alcohol could be purified by distillation under reduced pressure (boiling point 93 C./35 mm.). The yield was 239 g., corresponding to 96% of the theory, referred to the nitrate used initially. According to gas chromatographical tests, the fluorine-containing alcohol was found to be identical with the product described in German Pat. 1,214,660, Example 1, (purity 99.4%).

EXAMPLE 3 (a) 120 ml. of 98% nitric acid (2.80 moles) were added dropwise, at 85 C., while stirring, within 3 hours, to 400 g. (0.697 mole) of n-C F C I-I I, and the mixture was then stirred for 8 hours at 90 C. Working up of the reaction mixture was effected as described in Examples 1 and 2. After evaporation of the solvent a reddish, solid, crude product remained behind which could be purified by distillation under reduced pressure at 100-105 C./10 mm. Yield 340 g. 93% of the theory (iodine content 0.1%

Analysis:

N calculated for C H F NO =2.7; N found 2.5%

g. mole) Of Il-CgF qCzH4ONO to gether with 830 g. of methanol and 21 g. of Raney nickel were filled into an autoclave having a capacity of 2.5 liters and being lined with silver. After several rinsings with N and H at first H with a pressure of 30 atmospheres gauge was introduced and the whole was heated within 2 hours to 90 C. When this temperature was reached the pressure of hydrogen was increased to 50 atmospheres gauge and the autoclave was shaken for 6 hours at constant hydrogen pressure. Working up of the hydrogenation mixture was then carried out as described under Example 2. 273 g. 294% of the theory of II-C3F17C2H4OH (boiling point 95-96 C./l1 mm.) were obtained. According to gas chromatographical tests, the product was found to be identical with the product obtained according to German Pat. 1,214,660, Example 2, H'CaF17C2II4OH (purity 99.9%).

Analysis:

OH number calculated for C I-I F O=121; OH number found 120 EXAMPLE 4 (a) 400 g. of n-C F C I-IJ (0.594 mole) were combined at 85 C., while stirring, within 3 hours with 102 ml. of 98% nitric acid (2.38 moles). The whole was then stirred for 8 hours at 85 C. Working up of the reaction product was effected as described in Examples 2 and 3. After removal of the solution, 322 g. 389.2%

6 of the theory of crude n-C F C H ONO remained behind.

(b) 322 g. of the crude n-C F C H ONO (washed with water until free from acid) so prepared together with 950 g. of methanol and 18 g. of Raney nickel were introduced into an autoclave having a capacity of 2.5 liters. After rinsing with N and H hydrogen having a pressure of 30 atmospheres gauge was introduced and the pressure vessel was heated to 90 C. The hydrogen pressure was then increased to 50 atmospheres gauge. After 4 hours the hydrogenation was completed and the reaction mixture was worked up as described in Examples 2 and 3. 284 g. 95% of the theory of n-C F C H OH (boiling point l08ll7 C./1l12 mm. Hg) were obtained.

Analysis:

OH number, calculated for C H F O=99.5; OH number found==100 EXAMPLE 5 Example 3a was repeated in varying the concentration of the nitric acid used within the range of 65-98% and the reaction temperatures from 70-90 C. The results are compiled in the following Table 2 Yield of n-CaFnCzILONOz Concentration Reaction referred to of HNO3 in temperature ll-CgF CZHJ (percent percent C.) of the theory) 1 No reaction. 3 About.

EXAMPLE 6 Comparative test (preparation of n-C F C H -ONO from I1-C6F13C2H4OH):

3.0 ml. of 98% HNO were added dropwise, while stirring, at 60 C., Within 5 minutes to 11.5 g. (0.0316 mole) of n-C F C H 0H, and the mixture was then stirred for 20 minutes at 60 C. The ester was then separated by means of water, washed several times with water and distilled (boiling point 72-77 C./11 mm.).

EXAMPLE 7 A mixture of 27.5 g. (0.054 mole) of s 17( 2)2 2, 75 g. of pure methanol and 2 g. of Raney nickel was reacted at 60 C. at a pressure of 1 atmosphere for 14 hours with gaseous hydrogen. The yield of n-C F C H OH was 19.0 g. E 76% of the theory.

EXAMPLE 9 Example 3b was repeated in varying the temperature during hydrogenation within the range of from 6090 C. (cf. Table 3). The reaction time was 6 hours.

Table 3 Reaction Yield in percent of n-C F C H OH temperature, C. referred to I'l-CgF C H ONO2 used 7 EXAMPLE Example 3a was repeated using a molar proportion of n-C F C H I to 98% NHO' of 1:3. In contradistinction to Example 3a, the reaction mixture contains non-reacted n-C F C H I, at the rate Of 7% EXAMPLE 11 100 g. (0.174 mole) of n-C F C H I were added slowly, while stirring, within minutes to 200 ml. (4.77 moles) of 98% HNO at C. The whole was then stirred for hour at 70 C. After cooling, the fluorinecontaining nitrate formed was separated by means of 200 ml. of H 0 and taken up in CH CI The organic solution was washed until it was free from acid, dried and the solvent was removed by distillation. The fluorine-containing crude ester remaining behind was purified by distillation. The yield was 70 g. E 86% Of the theory Of Il-C F17C2H4ONO2.

We claim:

1. In a process for the preparation of an alcohol of the formula in which R is perfluoroalkyl of 4 to 16 carbon atoms, from an iodide of the formula in which R; is as defined above, by interaction of a mineral acid, the improvement comprising reacting said iodide in a first step with at least the three-fold molar amount of nitric acid of about to about 98% strength at a temperature of about 60 to about 100 C. to yield an ester of the formula in which R, is as defined as above, washing said ester until free of acid and hydrogenating in a second step said esters in the presence of Raney nickel as catalyst at a temperature of about 50 to about 100 C. and at a pressure of about 0 to about 100 atm. g.

2. The process as claimed in claim 1, in which iodides are reacted, the R, moiety of which is n-perfluoroalkyl of 4 to 16 carbon atoms.

3. The process as claimed in claim 1, in which iodides are reacted, the R moiety of which is perfiuoroalkyl of 4 to 10 carbon atoms.

4. The process as claimed in claim 1, in which the reaction temperature of the first step is about 60 to about C.

5. The process as claimed in claim 1, in which the molar ratio of iodide to nitric acid is in the range of about 1:3 to about 1:8.

6. The process as claimed in claim 1, in which the molar ratio of iodide to nitric acid is in the range of about 1:4.

7. The process as claimed in claim 1, in which the nitric acid is dropped to the liquid or molten iodide.

8. The process as claimed in claim 1, in which the iodide is added portionwise to the reaction vessel precharged with nitric acid.

9. The process as claimed in claim 1, in which the hydrogenation temperature is in the range of about 60 to about 90 C.

10. The process as claimed in claim 1, in which the hydrogenation is performed at a pressure of about 30 to about 50 atm. g.

References Cited UNITED STATES PATENTS 3,246,030 4/1966 Seil et a1. 260-633 3,283,012 11/1966 Day 260-633 FOREIGN PATENTS 202,098 9/1967 U.S.S.R 260-467 HOWARD T. MARS, Primary Examiner OTHER REFERENCES Khun, J. Chem. Soc., 68, pp. 1761-1762, 1946.

U.S. Cl. X.R. 260-467 

